Extremely Low-Frequency Magnetic Field as a Stress Factor-Really Detrimental?-Insight into Literature from the Last Decade

Biological effects of extremely low-frequency magnetic field (ELF-MF) and its consequences on human health have become the subject of important and recurrent public debate. ELF-MF evokes cell/organism responses that are characteristic to a general stress reaction, thus it can be regarded as a stress factor. Exposure to ELF-MF "turns on" different intracellular mechanisms into both directions: compensatory or deleterious ones. ELF-MF can provoke morphological and physiological changes in stress-related systems, mainly nervous, hormonal, and immunological ones. This review summarizes the ELF-MF-mediated changes at various levels of the organism organization. Special attention is placed on the review of literature from the last decade. Most studies on ELF-MF effects concentrate on its negative influence, e.g., impairment of behavior towards depressive and anxiety disorders; however, in the last decade there was an increase in the number of research studies showing stimulating impact of ELF-MF on neuroplasticity and neurorehabilitation. In the face of numerous studies on the ELF-MF action, it is necessary to systematize the knowledge for a better understanding of the phenomenon, in order to reduce the risk associated with the exposure to this factor and to recognize the possibility of using it as a therapeutic agent.

Comparison of polymerization and structural behavior of microtubules in rat brain and sperm affected by the extremely low-frequency electromagnetic field

Background

Microtubule proteins are able to produce electromagnetic fields and have an important role in memory formation, and learning. Therefore, microtubules have the potential to be affected by exogenous electromagnetic fields. This study aimed to examine the comparison of microtubule polymerization and its structural behavior in brain and sperm affected by 50 Hz extremely low-frequency electromagnetic field (ELEF).

Results

Twenties adult male rats were randomly and equally divided into control and experimental groups, to evaluate the effect of 50 Hz ELEF on the sperm and brain functions. Plus-maze, serum testosterone and corticosterone, and sperm evaluation were performed. Next, the semen and brain samples were obtained, and they were divided into four experimental groups for investigation of microtubule polymerization. There was no significant difference in testosterone and, corticosterone levels, anxiety behaviors, and sperm morphology between control and ELEF-exposure groups. The sperm viability, total and progressive motility were significantly higher in the ELEF-exposed group than that of the control group. The microtubule polymerization in sperm ELEF was significantly higher than in other groups. The secondary and tertiary structures of tubulins were significantly affected in the brain, and sperm ELEF groups.

Conclusion

It seems that the polymerization of microtubules and conformational changes of tubulin dimers are improved by ELEF application.

Effects of prenatal exposure to a 50-Hz magnetic field on one-trial passive avoidance learning in 1-day-old chicks

We investigated memory impairment in newly hatched chicks following in ovo exposure to a 50-Hz magnetic field (MF) of 2 mT (60 min/day) on embryonic days 12-18. Isolated and paired chicks were used to test the effect of stress during training, and memory retention was tested at 10, 30, and 120 min, following exposure to a bitter-tasting bead (100% methylanthranilate). Results showed that memory was intact at 10 min in both isolated and paired chicks with or without MF exposure. However, while isolated chicks had good memory retention levels at 30 and 120 min, those exposed to MF did not. The results suggest a potential disruption of memory formation following in ovo exposure to MF, with this effect only evident in the more stressed, isolated chicks.

Pre-sowing magnetic treatments of tomato seeds increase the growth and yield of plants

The effects of pre-sowing magnetic treatments on growth and yield of tomato (cv Campbell-28) were investigated under field conditions. Tomato seeds were exposed to full-wave rectified sinusoidal non-uniform magnetic fields (MFs) induced by an electromagnet at 100 mT (rms) for 10 min and at 170 mT (rms) for 3 min. Non-treated seeds were considered as controls. Plants were grown in experimental plots (30.2 m(2)) and were cultivated according to standard agricultural practices. During the vegetative and generative growth stages, samples were collected at regular intervals for growth rate analyses, and the resistance of plants to geminivirus and early blight was evaluated. At physiological maturity, the plants were harvested from each plot and the yield and yield parameters were determined. In the vegetative stage, the treatments led to a significant increase in leaf area, leaf dry weight, and specific leaf area (SLA) per plant. Also, the leaf, stem, and root relative growth rates of plants derived from magnetically treated seeds were greater than those shown by the control plants. In the generative stage, leaf area per plant and relative growth rates of fruits from plants from magnetically exposed seeds were greater than those of the control plant fruits. At fruit maturity stage, all magnetic treatments increased significantly (P < .05) the mean fruit weight, the fruit yield per plant, the fruit yield per area, and the equatorial diameter of fruits in comparison with the controls. At the end of the experiment, total dry matter was significantly higher for plants from magnetically treated seeds than that of the controls. A significant delay in the appearance of first symptoms of geminivirus and early blight and a reduced infection rate of early blight were observed in the plants from exposed seeds to MFs. Pre-sowing magnetic treatments would enhance the growth and yield of tomato crop.

Magnetoreception in plants

This article reviews phenomena of magnetoreception in plants and provides a survey of the relevant literature over the past 80 years. Plants react in a multitude of ways to geomagnetic fields-strong continuous fields as well as alternating magnetic fields. In the past, physiological investigations were pursued in a somewhat unsystematic manner and no biological advantage of any magnetoresponse is immediately obvious. As a result, most studies remain largely on a phenomenological level and are in general characterised by a lack of mechanistic insight, despite the fact that physics provides several theories that serve as paradigms for magnetoreception. Beside ferrimagnetism, which is well proved for bacterial magnetotaxis and for some cases of animal navigation, two further mechanisms for magnetoreception are currently receiving major attention: (1) the "radical-pair mechanism" consisting of the modulation of singlet-triplet interconversion rates of a radical pair by weak magnetic fields, and (2) the "ion cyclotron resonance" mechanism. The latter mechanism centres around the fact that ions should circulate in a plane perpendicular to an external magnetic field with their Lamor frequencies, which can interfere with an alternating electromagnetic field. Both mechanisms provide a theoretical framework for future model-guided investigations in the realm of plant magnetoreception.

Response of cyclic AMP by DMSO differentiated HL-60 cells exposed to electric interferential current after prestimulation

The action of interferential current (IFC) upon intracellular content of cyclic adenosine monophosphate (cAMP) after prestimulation with the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) has been investigated. Human promyelocytes (HL-60) differentiated to granulocytes by dimethylsulphoxide (DMSO) have been treated with different concentrations of fMLP. This enhances their cAMP content. The half maximal effective concentration (EC50) was about 4 nM. Exposure to IFC with modulation frequencies of 35 and 125 Hz (5 min, 250 microA/cm2) after prestimulation with various concentrations of fMLP had no enhancing effect at low or high concentrations of fMLP. In contrast, at medium concentrations in the range of about 100 pM fMLP, a significant enhancement of cAMP could be observed. This synergistic effect of fMLP and IFC has been examined in detail by varying the modulation frequency, current density, and exposure time. Enhancement of cAMP content could be observed at certain modulation frequencies and exposure times suggesting a window effect, whereas for the current density in the range measured (8.5 microA/cm2-2.5 mA/cm2) a constant enhancement could be observed. The synergistic effect of fMLP and IFC could only be observed in the treatment sequence of fMLP followed by IFC; an inverse sequence had no effect on the cAMP content. .

Weak electromagnetic fields (50 Hz) elicit a stress response in human cells

The aim of this study was to demonstrate the expression of heat shock (HS) genes in human cells in response to extremely low-frequency electromagnetic fields (ELF-EMF) alone and in combination with thermal stress. After exposing human myeloid leukemia (HL-60) cells to the stressor(s) for 30 min we quantified the expression of the HS genes HSP27, HSP60, HSP70 (A, B, and C), HSC70, HSP75, HSP78, and HSP90 (alpha and beta) by RT-PCR. The results clearly show that HS genes, in particular the three HSP70 genes (A, B, and C), are induced by ELF-EMF, a reaction that is enhanced by simultaneous HS (43 degrees C for 30 min). The results show similarities and some significant differences to previous experiments in which transgenic nematodes were used to monitor the induction of the HSP70 gene under similar stress conditions. We also studied the effect of different flux densities on gene expression in the range of 10-140 microT. Even the lowest dose tested (10 microT) resulted in a significant induction of the genes HSP70A, HSP70B, and HSP70C. The reaction to ELF-EMF shows a maximum at a flux density of 60-80 microT. The unusual dose-response relation reveals an interesting difference to other stressors that elicit the HS response.

Low-frequency electromagnetic fields induce a stress effect upon higher plants, as evident by the universal stress signal, alanine

15N NMR analysis reveals alanine production in Duckweed plants exposed to low intensity sinusoidally varying magnetic fields (SVMF) at 60 and 100Hz, and fed by 15N-labeled ammonium chloride. Alanine does not accumulate in the absence of SVMF. Addition of vitamin C, a radical scavenger, reduced alanine production by 82%, indicating the roll of free radicals in the process. Alanine accumulation in plants and animals in response to exposure to a variety of stress conditions, including SVMF, is a general phenomenon. It is proposed that alanine is a universal first stress signal expressed by cells.